Copper(I)-catalyzed chlorine atom transfer radical cyclization reactions of unsaturated alpha-chloro beta-keto esters.

Copper(I) chloride catalyzed chlorine atom transfer radical cyclization reactions of a series of olefinic alpha-chloro beta-keto esters were investigated. It was found that alpha-dichlorinated beta-keto esters were suitable substrates; the chlorine transfer mono or tandem radical cyclization reactions catalyzed by CuCl complex with bis(oxazoline) or bipyridine proceeded smoothly in dichloroethane at room temperature or 80 degrees C, providing cyclic and bicyclic compounds in moderate to high yield. [reaction: see text]

Ni(II)-catalyzed Conia-ene reaction of 1,3-dicarbonyl compounds with alkynes.

[reaction: see text]. We have discovered a Ni(II)-catalyzed Conia-ene reaction of 1,3-dicarbonyl compounds with alkynes. In the presence of Ni(acac)2 and Yb(OTf)3, various acetylenic 1,3-dicarbonyl compounds underwent Conia-ene reaction to give mono- and bicyclic olefinic cyclopentanes. A mechanism involving the enol-yne-Ni complex formation is proposed and supported by deuterium-labeling experiments.

Et2AlCl-promoted asymmetric phenylseleno group transfer radical cyclization reactions of unsaturated beta-hydroxy esters.

We have developed a new method for asymmetric phenylseleno group transfer radical cyclization of unsaturated beta-hydroxy esters. Various unsaturated alpha-phenylseleno beta-hydroxy esters underwent radical cyclization in the presence of Et(2)AlCl in benzene with sunlamp irradiation at 25-30 degrees C to give mono- and bicyclic group-transferred products in an efficient and highly regioselective and diastereoselective manner. To rationalize the high diastereoselectivities observed in this reaction, we propose a model based on chelation control of the aluminum alkoxides that are formed in situ. We devised a general method to prepare chiral radical precursors from which we obtained highly optically pure mono- and bicyclic group transfer products. The synthetic advantages of this method are demonstrated by our formal total synthesis of (-)-wilforonide. This paper presents the first examples of stereoselective group transfer radical cyclizations that occur via 1,2-asymmetric induction.